Hairy leukoplakia (HL) is an Epstein Barr Virus (EBV)-associated oral lesion found predominantly in HIV-positive individuals. This lesion represents the only instance in which active replication of EBV is known to occur in epithelial tissues, and is characterized by a unique set of histopathologic features that include nuclear inclusions, ballooning degeneration, and parakeratosis. Evidence is accumulating that EBV gene expression in epithelial cells may differ significantly from that of lymphocytes. While much is known about the latter, the molecular biology of EBV in epithelial tissues, and in HL in particular, are poorly understood. The repertoire and structure of EBV gene transcripts in HL tissues, the effects of EBV proteins on epithelial cell biology, the regulation of these proteins, and the role of these proteins in the pathogenesis of HL remain undefined. The goal of this project is to begin to understand the role of EBV in the pathogenesis of HL. We will characterize the repertoire of gene products expressed by EBV in HL tissues and analyze the structure of EBV transcripts. We will then transfect individual EBV genes expressed in HL tissues into primary keratinocytes, and will study the effects of these genes in monolayer tissue culture, as well as their effects on epithelial cell differentiation by studying the keratinocytes on "floating rafts". Lastly, we will identify putative promotors of these transcripts, determine if these promotors are active in epithelial cells, and determine if promotor usage is epithelial cell-specific. HL represents a model in which normally nonpathogenic viruses and other agents may induce disease in the setting of HIV-induced immune suppression. To begin to understand the mechanisms of this interaction, a thorough understanding of HL is of great importance. Together, these studies will provide a significant amount of information on the molecular biology of EBV and its role in the pathogenesis of HL. These studies also afford an important opportunity to better understand EBV infection of the epithelium in general, and most importantly, they lay a foundation for future studies of the role of immune suppression in modulation of viral gene expression as a model for the development of HIV-associated opportunistic disease.